Inventory and Assemblage Classification of the Freshwater Mussels (Mollusca: Unionidae) of the Strawberry River, Arkansas, USA, with Implications for Conservation Planning

Abstract

Spatial hierarchical approaches to classify freshwater systems can add to our understanding of biogeographical patterns and can be used for biodiversity conservation planning. The Strawberry River is located primarily in the Ozark Highlands Central Plateau of north central Arkansas, USA, with a small downstream portion in the Mississippi Alluvial Plain and has been designated an Extraordinary Resource Water, an Ecologically Sensitive Water Body, and a Natural Scenic Waterway. The goals of this study were to document Strawberry River, Arkansas freshwater mussels to aid in conservation planning. Our first objective was to inventory freshwater mussel species in the Strawberry River. Our second objective was to use this stream-wide dataset to classify the freshwater mussel assemblages. We used unpublished survey data of 59 sites distributed from the headwaters to the mouth to inventory species occurrence and abundance, classified mussel assemblages using non-metric multi-dimensional scaling (NMS), and conducted indicator species analysis on resulting assemblages. We observed 39 taxa across the 59 survey sites including two S1, five S2, 16 S3, 11 S4, four S5, and one state non-ranked conservation rank species. Furthermore, our assemblage NMS revealed two distinct freshwater mussel assemblages roughly organized by an upstream (Sites 1–31) to downstream (Sites 32–59) gradient. There were five upstream indicator species and 13 downstream indicator species. This study provides a case study on using existing datasets with NMS and indicator species analyses to classify mussel assemblages and adds to our understanding of freshwater mussel fauna classification at smaller spatial scales. Both NMS and indicator species outcomes can aid in conservation planning for freshwater mussels.

One informs the other: Unionid species at risk and benthic macroinvertebrate community monitoring data are complementary

“…The identification of benthic macroinvertebrate indicator taxa for Endangered and Threatened mussel species is a novel finding of this study and offers a new application for existing data sets and monitoring programs (e.g., assisting the identification of critical habitat). Macroinvertebrates as indicators could provide significant utility value for mussel conservation and extend the identification of associations among mussel species (Christian et al 2021) of Endangered and Threatened mussel species as well as the specific occurrence of Ptychobranchus fasciolaris (Kidneyshell) and Epioblasma triquetra (Snuffbox). Leptohyphidae mayflies were also associated with the presence of Endangered and Threatened mussel species as well as the specific occurrence of Cyclonaias tuberculata (Purple Wartyback), Epioblasma rangiana, Epioblasma triquetra, Ptychobranchus fasciolaris, and Pleurobema sintoxia (Round Pigtoe).…”

“…To assess the variation of overall mussel community composition among sites where listed SAR were present and where they were not, a Nonmetric Multidimensional Scaling ordination was run for the combined data set using Bray-Curtis dissimilarity distance (Faith et al 1987;Christian et al 2021). The significance of differences in mussel commu-nity composition between sites where SAR were present and where they were absent was evaluated using a permutational analysis of variance (PERMANOVA) with 999 permutations.…”

“…Diversity metrics were compared to mussel species richness among sites using generalized linear models employing a Poisson error distribution. Finally, benthic macroinvertebrate taxa indicative of the presence of Endangered or Threatened mussel species were identified using Indicator Taxa Analysis (ITA) involving evaluating the presence/absence of macroinvertebrate taxa against the presence of Endangered or Threatened mussel species found in the field survey (Dufre ˆne and Legendre 1997; Christian et al 2021).…”